Primer composition and bonding method

ABSTRACT

This invention provides a primer composition comprising the following (A), (B), (C) and (D) components: 
     (A) a saturated hydrocarbon polymer having at least one alkenyl group per molecule, 
     (B) a silane coupling agent, 
     (C) a polyvalent alkoxysilane and/or a condensation product thereof, and 
     (D) an organoaluminum compound and/or an organotitanium compound.

FIELD OF THE INVENTION

The present invention relates to a primer composition effective inbonding an addition reaction type hydrocarbon polymer securely tovarious substrates. More particularly, the invention relates to a primertechnology for achieving improved bonds to substrates and a technologyof improving the adhesion of an addition type cured product whichcomprises coating a primer on a substrate and then applying an additionreaction type curable composition comprising a hydrocarbon polymerthereon and letting it cure in situ.

BACKGROUND OF THE INVENTION

A curable resin (also known as an addition type curable composition) inwhich a hydrocarbon polymer containing at least one alkenyl group withinits molecule is crosslinked with a curing agent having two or moresilicon-bound hydrogen atoms per molecule has been disclosed in JapaneseKokai Publication Hei-2-75644 and Japanese Kokai PublicationHei-3-181565, for instance. The cured product derived from such acomposition (which artifact is also known as an addition type curedproduct) has excellent weather resistance, high heat resistance and lowmoisture permeability and, therefore, is expected to find application ina broad spectrum of end uses.

Particularly when an addition type curable composition comprising ahydrocarbon polymer is used as a coating or dipping agent or a sealantfor various substrates, it must have a high adhesiveness for the varioussubstrates. The known technology of imparting adhesiveness to such anaddition type curable composition comprising a hydrocarbon polymerinvolves addition of various adhesion-improving agents to an additiontype curable composition. By way of illustration, Japanese KokaiPublication Hei-4-185687 discloses a technique comprising adding asilane coupling agent to an addition type curable composition; JapaneseKokai Publication Hei-08-134165 discloses a technique comprising addinga nitrogen-containing epoxy compound and a silane coupling agent;Japanese Kokai Publication Hei-08-134165 discloses a techniquecomprising adding an isocyanate-containing compound and a silanecoupling agent; Japanese Kokai Publication Hei-09-316293 and JapaneseKokai Publication Hei-10-204222 disclose a technology comprising addinga silane coupling agent, an alkoxysilane condensate and anorganoaluminum and/or organotitanium compound. These techniques have thedisadvantage, inter alia, that, depending on the kind of silane couplingagent, a retardation of cure may take place.

SUMMARY OF THE INVENTION

The object of the invention is to provide a primer composition which iseffective in achieving a firm bond between a various substrate and acured product derived from a hydrosilylation-curable compositioncomprising a hydrocarbon polymer containing at least one alkenyl groupper molecule and a curing agent having two or more hydrogen atoms boundto silicon per molecule and to provide a bonding method.

Landing on a concept representing a complete departure from he priorart, the inventors of the present invention discovered that an additiontype curable composition comprising a hydrocarbon polymer containing atleast one alkenyl group per molecule and a curing agent having two ormore hydrogen atoms bound to silicon per molecule and a cured productderived therefrom can be bonded to various substrates by utilizing aprimer composition.

The present invention, therefore, is concerned with a primer compositioncomprising the following (A), (B), (C) and (D) components:

(A) a hydrocarbon polymer containing at least one alkenyl group permolecule

(B) a silane coupling agent

(C) a polyvalent alkoxysilane and/or a condensation product thereof, and

(D) an organoaluminum compound and/or an organotitanium compound.

The present invention is further concerned with a primer compositioncomprising the following (E) component in addition to said (B), (C) and(D) components:

(E) a vinyl copolymer having a backbone structure substantiallycomprised of a vinyl copolymer chain and containing a silicon-containinggroup having a hydroxyl or hydrolyzable group bound to a silicon atomand capable of crosslinking by siloxane bonding terminally of itsbackbone and/or side chain.

In this invention, the preferred (E) component vinyl copolymer has anumber average molecular weight in the range of 500 to 50000 andcontains a hydrolyzable silyl group of the general formula (1)terminally of its backbone and/or side chain.

in which R¹ and R²each independently represents an alkyl group of 1 to20 carbon atoms, an aryl group of 6 to 20 carbon atoms, an aralkyl groupof 7 to 20 carbon atoms, or a triorganosiloxy group of the formula(R′)₃SiO—, where R′ groups each independently represents a substitutedor unsubstituted hydrocarbon group containing 1 to 20 carbon atoms; Xgroups each independently represents a hydroxyl group or a hydrolyzablegroup; a denotes 0, 1, 2 or 3; b denotes 0, 1 or 2; but both a and b arenot equal to 0; m denotes an integer of 0 to 19.

A further preferred composition comprises a hydrocarbon polymercontaining at least one alkenyl group per molecule, that is said (A)component, in addition to said (B) to (E) components.

More preferably, in this invention, the (A) component hydrocarbonpolymer is a polyisobutylene polymer having a number average molecularweight in the range of 500 to 50000 and containing at least one alkenylgroup terminally of its backbone and/or side chain.

Moreover, in this invention, the (B) component silane coupling agent isa silane coupling agent having at least one of epoxy group, a vinylgroup and a (meth)acryloyl group, and may advantageously be a mixture oftwo or more specific silane coupling agents.

In addition, a further preferred primer composition of the inventioncomprises a hydrosilylation catalyst as (F) component.

The present invention is further directed to a bonding method forbonding a cured product to a substrate

which comprises coating a primer composition comprising a silanecoupling agent as said (B) component on a substrate

and then applying a curable composition comprising a hydrocarbon polymerhaving at least one alkenyl group per molecule onto the primedsubstrate.

In this invention, it is preferable to formulate a polyvalentalkoxysilane and/or a condensation product thereof as (C) component andan organoaluminum compound and/or an organotitanium compound as (D)component in addition to said (B) component. Furthermore, it ispreferable to add a hydrosilylation catalyst as (F) component and stillmore preferably add an organic solvent as (G) component.

The invention is further concerned with a bonding method for bonding acured product to a substrate

which comprises coating a primer composition comprising a polyvalentalkoxysilane and/or a condensation product thereof as (C) component andan organoaluminum compound and/or an organotitanium compound as (D)component on a substrate

and then applying a curable composition comprising a hydrocarbon polymerhaving at least one alkenyl group per molecule to the primed substrate.

Preferably, in this invention, said hydrocarbon polymer having at leastone alkenyl group per molecule is a polyisobutylene polymer containingat least one alkenyl group terminally of its backbone and/or side chainand having a number average molecular weight in the range of 500 to50000.

Furthermore, in this invention, the (B) component silane coupling agentis one or more kinds of silane coupling agent(s) containing an epoxygroup, a vinyl group or a (meth)acryloyl group.

The invention is further concerned with a laminate comprising asubstrate and a cured product as obtainable by the above bonding method.

DETAILED DESCRIPTION OF THE INVENTION

The primer composition and addition type curable composition which areto be used in the practice of the present invention are now described indetail.

The (A) component for use in the invention is a hydrocarbon polymerhaving at least one hydrosilylatable alkenyl group within its molecule.The hydrosilylatable alkenyl group is not particularly restricted as faras it is a group containing a carbon-carbon double bond active forhydrosilylation. As such alkenyl groups, there may be mentionedaliphatic unsaturated hydrocarbon groups such as vinyl, allyl,methylvinyl, propenyl, butenyl, pentenyl, hexenyl, etc. and cyclicunsaturated hydrocarbon groups such as cyclopropenyl, cyclobutenyl,cyclopentenyl, cyclohexenyl and so on. In the present invention, the (A)component preferably has 1 to 10 alkenyl groups per molecule.

The polymer constituting the backbone of the (A) component hydrocarbonpolymer can be prepared by, for example,

(1) polymerizing an olefinic compound containing 1 to 6 carbon atoms,such as ethylene, propylene, 1-butene, isobutylene and the like, as amain monomer or

(2) homopolymerizing a diene compound, such as butadiene, isoprene andthe like, or copolymerizing said olefinic compound with said dienecompound, followed by hydrogenation. In terms of the ease with which afunctional group may be introduced terminally of the polymer, themolecular weight of the polymer be well controlled, and the number ofterminal functional groups be increased, an isobutylene polymer, ahydrogenated polybutadiene polymer or a hydrogenated polyisoprenepolymer is preferred.

The isobutylene polymer mentioned above may be exclusively composed ofisobutylene or may contain a unit monomer or monomers copolymerizablewith isobutylene in a proportion of preferably not more than 50% (% byweight; the same applies hereinafter), more preferably not more than30%, most preferably not more than 20%.

As such unit monomers, there can be mentioned olefins of 4 to 12 carbonatoms, vinyl ethers, aromatic vinyl compounds, vinylsilanes,allylsilanes and so on. Specific examples are 1-butene, 2-butene,2-methyl-1-butene, 3-methyl-1-butene, pentene, 4-methyl-1-pentene,hexene, vinylcyclohexane, methyl vinyl ether, ethyl vinyl ether,isobutyl vinyl ether, styrene, α-methylstyrene, dimethylstyrene,p-t-butoxystyrene, p-hexenyloxystyrene, p-allyloxystyrene,p-hydroxystyrene, β-pinene, indene, vinyldimethylmethoxysilane,vinyltrimethylsilane, divinyldimethoxysilane, divinyldimethylsilane,1,3-divinyl-1,1,3,3-tetramethyldisiloxane, trivinylmethylsilane,tetravinylsilane, allyldimethylmethoxysilane, allyltrimethylsilane,diallyldimethoxysilane, diallyldimethylsilane,γ-methacryloyloxypropyltrimethoxysilane andγ-methacryloyloxypropylmethyldimethoxysilane, among others.

The hydrogenated polybutadiene polymer or other hydrocarbon polymer mayalso contain unit monomers other than the main monomer just as saidisobutylene polymer.

The hydrocarbon polymer for use as (A) component in the invention may beprepared using a monomer component leaving a double bond afterpolymerization, such as a polyene compound, e.g. butadiene, isoprene orthe like, in a proportion not jeopardizing the object of the invention,i.e. in a small proportion, preferably within the range of not more than10%.

The hydrocarbon polymer, preferably an isobutylene polymer, ahydrogenated polyisoprene polymer or a hydrogenated polybutadienepolymer, preferably has a number average molecular weight (GPC method;polystyrene equivalent) of not more than 100000, more preferably about500 to 100000. In consideration of the ease of handling, a liquidpolymer having sufficient fluidity with a molecular weight of about 1000to 40000 is particularly preferred.

The technology of preparing (A) component for use in the inventionincludes a method comprising reacting a polymer having a hydroxyl orother functional group with a compound having an unsaturated group tointroduce the unsaturated group into the polymer as described inJapanese Kokai Publication Hei-3-152164 or Japanese Kokai PublicationHei-7-304909. There may also be mentioned a Friedel-Crafts reactionmethod using an alkenyl phenyl ether to introduce an unsaturated groupinto a halogen-containing polymer, a substitution reaction method usingan allyltrimethylsilane or the like in the presence of a Lewis acid, anda method comprising carrying out a Friedel-Crafts reaction with a phenolcompound to introduce a hydroxyl group and, then, carrying out the abovealkenyl group-introducing reaction. It is also possible to use methodsin which unsaturated groups are introduced in the course ofpolymerization of the monomer as disclosed in U.S. Pat. No. 4,316,973,Japanese Kokai Publication Sho-63-105005 and Japanese Kokai PublicationHei-4-288309.

The silane coupling agent for use as (B) component in the invention ispreferably a silane coupling agent having a silicon-bound alkoxy groupand at least one functional group selected from the group consisting ofepoxy, methacryl, acryl, isocyanate, isocyanurate, vinyl and carbamategroups. Among said functional groups, one having an epoxy, vinyl,methacryl or acryl group in the molecule is particularly preferred fromthe standpoint of curability and adhesion. Specifically, there can bementioned such organosilicon compounds having an epoxy functional groupand silicon-bound alkoxy groups as 3-glycidoxypropyltrimethoxysilane,3-glycidoxypropyltriethoxysilane,2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and2-(3,4-epoxycyclohexyl)ethyltriethoxysilane. As organosilicon compoundshaving a vinyl group and silicon-bound alkoxy groups, there can bementioned vinyltrimethoxysilane and vinyltriethoxysilane, among others.Furthermore, as organosilicon compounds having a methacryl or acrylgroup and silicon-bound alkoxy groups, there can be mentioned3-methacryloxypropyltrimethoxysilane,3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane,3-acryloxypropyltriethoxysilane, methacryloxymethyltrimethoxysilane,methacryloxymethyltriethoxysilane, acryloxymethyltrimethoxysilane,acryloxymethyltriethoxysilane and so on.

While the polyvalent alkoxysilane for use as (C) component in theinvention has only those groups selected from among alkyl and alkoxygroups as substituents on the silicon atom, its partial hydrolysate anda dehydrative condensation product thereof (silanol condensationproduct) is also included. As specific examples of the polyvalentalkoxysilane for (C) component, there can be mentionedtetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane,tetra(n-propyloxy) silane, tetra(n-butoxy)silane, etc., inclusive oftheir condensation products, and trialkoxysilanes such asmethyltriethoxysilane, ethyltriethoxysilane, etc., inclusive of theircondensation products.

The condensation catalyst for use as (D) component in the inventionincludes organoaluminum compounds and organotitanium compounds.Preferred organoaluminum compounds are chelate organic complexes whichare acknowledged to be useful for catalyzing the hydrolytic condensationreaction of alkoxysilyl groups. As a specific example, there can bementioned aluminum acetylacetonate. The preferred organotitaniumcompound is an organotitanium compound containing a Ti—O—C bond which isacknowledged to be useful for catalyzing the hydrolytic condensationreaction of alkoxysilyl groups. More specifically, tetraalkoxytitaniumssuch as tetraisopropoxytitanium, tetrabutoxytitanium, etc., andgeneral-purpose titanate coupling agents such as those havinghydroxyacetic acid or ethylene glycol or the like as a residue can beemployed.

The vinyl copolymer having a reactive silicon-containing group for useas (E) component in the invention (hereinafter referred to assilyl-containing vinyl polymer) is a polymer whose backbone structure issubstantially comprised of a vinyl polymer chain and optionally having asegment other than the vinyl monomer segment, such as a segmentcomprising a urethane bond or a siloxane bond within the range notsubstantially affecting the characteristics of a vinyl polymer.Generally speaking, the properties characteristic of a vinyl polymer arenot affected materially even when the polymer contains a segment orsegments other than the segment composed of a vinyl monomer in aproportion of not more than about 50 atom % based on the total number ofatoms constituting its backbone chain. As the backbone chain is thuscomprised substantially of a vinyl polymer, said silyl-containingpolymer functions as a primer with good durability and resistance tochemicals, for instance.

The reactive silicon-containing group may for example represented by thegeneral formula (1):

wherein R¹ and R² each independently represents an alkyl group of 1 to20 carbon atoms, an aryl group of 6 to 20 carbon atoms, an aralkyl groupof 7 to 20 carbon atoms, or a triorganosiloxy group of the formula(R′)₃SiO—, where R′ groups each represents a substituted orunsubstituted C₁₋₂₀ hydrocarbon group; X groups each independentlyrepresents a hydroxyl group or a hydrolyzable group; a is equal to 0, 1,2 or 3; b is equal to 0, 1 or 2; although both a and b are not equal to0; m is an integer of 0 to 19.

The hydrolyzable group includes conventional groups such as hydrogen,halogen, alkoxy, acyloxy, ketoximato, amino, amido, aminooxy, mercapto,alkenyloxy, etc. Among these, alkoxy, amido and aminooxy are preferred.In terms of the hydrolyzability under mild conditions and ease ofhandling, alkoxy groups are particularly preferred.

The hydrolyzable group and/or hydroxyl group may be attached, in thenumber of 1 to 3, to one silicon atom and (a+Σb) is preferably withinthe range of 1 to 5. When two or more hydrolyzable groups or hydroxylgroups are present in the reactive silicon-containing group, thesegroups maybe the same or different.

While the number of silicon atoms constituting said reactivesilicon-containing group is at least one, it is preferably not more than20 at the maximum when silicon atoms are linked by siloxane bonding.

Particularly, a reactive silicon-containing group of the general formula(2) is preferred from availability points of view;

wherein R², X and a are as defined hereinbefore.

That said silyl-containing vinyl polymer has at least one hydrolyzablesilyl group terminally of its backbone and/or side chain means that thepolymer contains at least one hydrolyzable silyl group, preferably notless than two hydrolyzable silyl groups, per molecule at a terminus ofits main chain or at the terminus of its side chain. Because of thepresence of at least one hydrolyzable silyl group per molecule, thepolymer gains in molecular mass or undergoes gelation in the presence ofwater, forming chemically stable siloxane bonds to improve the chemicalresistance and other properties of the coating film. Moreover, thehydrolyzable silyl groups have a good affinity for inorganic substratesand undergo crosslinking in the presence of water so that an intimatebond can be established between the coating film and the inorganicsubstrate.

The preferred number average molecular weight of said silyl-containingvinyl polymer is about 500 to 50,000 and, in terms of the ease ofhandling, the range of about 1,000 to 20,000 is particularly preferred.

The glass transition point (Tg) of the polymer is not particularlyrestricted, either, but a low-shrinkage characteristic develops in thepolymer when its Tg is as low as 10° C. or still lower, while thechemical resistance, water resistance and substrate-reinforcing effectare improved when the Tg of the polymer is as high as 30° C. and above.

Various methods are available for the production of saidsilyl-containing vinyl polymer. For example, there can be mentioned (i)a method which comprises copolymerizing a vinyl monomer with ahydrolyzable silyl group-containing monomer (hereinafter referred to assilyl-containing monomer) and (ii) a method which comprisescopolymerizing a vinyl monomer with a monomer having a reactivefunctional group (hereinafter referred to as X group) [e.g. acrylicacid] and further reacting the resulting copolymer with a compoundhaving a reactive silicon-containing group and a functional groupcapable of reacting with the X group [e.g. a compound having anisocyanate group and a —Si(OCH₃) group].

The vinyl monomer mentioned just above is not particularly restrictedbut includes, among others, esters of unsaturated carboxylic acids, suchas methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate,isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth) acrylate, stearyl (meth)acrylate, benzyl(meth)acrylate, cyclohexyl (meth)acrylate, trifluoroethyl(meth)acrylate, pentafluoropropyl (meth)acrylate, diesters or hemiestersof polycarboxylic acids (maleic acid, fumaric acid, itaconic acid, etc.)with a straight-chain or branched-chain alcohols containing 1 to 20carbon atoms, etc.; aromatic hydrocarbon type vinyl compounds such asstyrene, α-methylstyrene, chlorostyrene, styrensulfonic acid,4-hydroxystyrene, vinyltoluene, etc.; vinyl esters and allyl compounds,such as vinyl acetate, vinyl propionate, diallyl phthalate, etc.;nitrile-containing vinyl compounds such as (meth)acrylonitrile;epoxy-containing vinyl compounds such as glycidyl (meth)acrylate;amino-containing vinyl compounds such as dimethylaminoethyl(meth)acrylate, diethylaminoethyl (meth)acrylate, vinylpyridine,aminoethyl vinyl ether, etc.; amido-containing vinyl compounds such as(meth)acrylamide, itaconic acid diamide, α-ethylacrylamide,methacrylamide, crotonamide, maleic acid diamide, fumaric acid diamide,N-vinylpyrrolidone, N-butoxymethyl (meth) acrylamide,N,N-dimethylacrylamide, N-methylacrylamide, acryloylmorpholine, etc.;hydroxy-containing vinyl compounds such as 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl vinylether, N-methylol meth)acrylamide, Aronix 5700 (product of Toa GoseiChemical Industry Co.), Placcel FA-1, Placcel FA-4, Placcel FM-1,Placcel FM-4 (products of Daicel Chemical Co.), etc.; unsaturatedcarboxylic acids and acid anhydrides, inclusive of their salts, such as(meth) acrylic acid, maleic acid, fumaric acid, itaconic acid, etc.,salts thereof (alkali metal salts, ammonium salts, amine salts, etc.),maleic anhydride, etc.; and other vinyl compounds such as vinyl methylether, vinyl chloride, vinylidene chloride, chloroprene, propylene,butadiene, isoprene, maleimide, N-vinylimidazole, vinylsulfonic acidsand so on. Among these, alkyl (meth)acrylates containing 10 or morecarbon atoms, such as lauryl (meth) acrylate and stearyl (meth)acrylate, are still more preferred because they provide for coats havinga good affinity even for a low-polarity curable composition containing ahydrocarbon polymer.

Thus, for producing a silyl-containing vinyl polymer with a low Tg valueof, for example, not higher than 10° C., it is only sufficient to use avinyl monomer which would give a homopolymer having a low Tg value, suchas butyl acrylate and 2-ethylhexyl (meth)acrylate, in a largeproportion. On the other hand, for producing a silyl-containing vinylpolymer with a high Tg value of, for example, 30° C. or higher, it isonly sufficient to use a vinyl monomer which would give a homopolymerhaving a high Tg value, such as methyl methacrylate, ethyl methacrylateand styrene.

The silyl-containing monomer mentioned above is not particularlyrestricted but includes the following compounds, among others.

CH₂═CHSi(OCH₃)₃ CH₂═CHSiCl₃

CH₂═CHCOO(CH₂)₃Si(OCH₃)₃

CH₂═CHCOO(CH₂)₃SiCl₃

CH₂═C(CH₃)COO(CH₂)₃Si(OCH₃)₃

CH₂═C(CH₃)COO(CH₂)₃SiCl₃

CH₂═C(CH₃)COO(CH₂)₃Si(OCH₂CH₃)₃

The technology of producing a silyl-containing vinyl polymer from such asilyl-containing monomer and a vinyl monomer is not particularlyrestricted but includes the production processes disclosed in JapaneseKokai Publication Sho-54-36395, Japanese Kokai Publication Sho-57-36109and Japanese Kokai Publication Sho-58-157810, among others. The solutionpolymerization technique using an azo type radical initiator such as2,2′-azobisisobutyronitrile or 2,2′-azobis(2-methylbutyronitrile) ismost preferred because the initiator can be easily handled and thepolymerization reaction mixture obtained can be utilized as it is.

Where necessary, in the above production procedure, molecular weightmodulation can be made using a chain transfer agent such asn-dodecylmercaptan, t-dodecylmercaptan, n-butylmercaptan,γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane,γ-mercaptopropylmethyldimethoxysilane,γ-mercaptopropylmethyldiethoxysilane, (CH₃O)₃Si—S—S—Si(OCH₃)₃,(CH₃O)₃Si—S₈—S—Si(OCH₃)₃ or the like.

Particularly, by using a chain transfer agent having a hydrolyzablesilyl group within its molecule, for exampleγ-mercaptopropyltrimethoxysilane, the hydrolyzable silyl group can beintroduced terminally of the resulting silyl-containing vinyl polymer.

As the polymerization solvent, non-reactive solvents such ashydrocarbons (e.g. toluene, xylene, n-hexane, cyclohexane, etc.), aceticacid esters (e.g. ethyl acetate, butyl acetate, etc.), alcohols (e.g.methanol, ethanol, isopropyl alcohol, n-butanol, etc.), ethers (e.g.ethyl Cellosolve, butyl Cellosolve, Cellosolve acetate, etc.) andketones (e.g. methyl ethyl ketone, ethyl acetoacetate, acetylacetone,diacetone alcohol, methyl isobutyl ketone, acetone, etc.) can be freelyused.

The amount of the silyl group-containing vinyl polymer in the primercomposition of the invention is preferably not less than 1%, morepreferably not less than 3%, still more preferably not less than 5%. Thesilyl group-containing vinyl polymer may be a single polymer species ora mixture of two or more polymer species.

The hydrosilylation catalyst for use as (F) component in the inventionis not particularly restricted but may be an arbitrary one.

For example, there can be mentioned chloroplatinic acid, platinum assimple substance, solid platinum as immobilized on an alumina, silica,carbon black or other support; platinum-vinylsiloxane complexes [e.g.Pt_(n)(ViMe₂SiOSiMe₂Vi)_(n), Pt[(MeViSiO)₄]_(m)]; platinum-phosphinecomplexes [e.g. Pt(PPh₃)₄, Pt(PBu₃)₄]; platinum-phosphite complexes[e.g. Pt[P(OPh)₃]₄, Pt[P(OBu)₃]₄ (In the above formulas, Me stands formethyl, Bu for butyl, Vi for vinyl, Ph for phenyl; n and m eachrepresents an integer), Pt(acac)₂, the platinum-hydrocarbon complexesdescribed in U.S. Pat. Nos. 3,159,601 and 3,159,662 issued to Ashby etal., and the platinum alcoholate catalyst described in U.S. Pat. No.3,220,972 issued to Lamoreaux et al.

As examples of the catalyst other than platinum compounds, there can bementioned RhCl (PPh₃)₃, RhCl₃, Rh/Al₂O₃, RuCl₃, IrCl₃, FeCl₃, AlCl₃,PdCl₂.2H₂O, NiCl₂, TiCl₄, and so on. These catalysts may be usedindependently or two or more of them may be used in combination. Interms of catalyst activity, chloroplatinic acid, platinum-olefincomplexes, platinum-vinylsiloxane complexes and Pt(acac)₂ are preferred.

The organic solvent for use as (G) component in the invention isintended to adjust the primer composition to a suitable viscosity forpriming. The solvent may be any solvent that is capable of dissolving(A) to (F) components and is not particularly restricted in kind. Asexamples, there can be mentioned hydrocarbon solvents such as toluene,xylene, heptane, hexane, petroleum solvents, etc.; halogen-containingsolvents such as trichloroethylene; ester solvents such as ethylacetate, butyl acetate, etc.; ketone solvents such as acetone, methylethyl ketone, methyl isobutyl ketone, etc.; silicon-containing solventssuch as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane,decamethylcyclopentasiloxane, etc., among others. These solvents may beused independently or two or more of them may be used in combination.

The curable composition which can be advantageously used in combinationwith the primer composition of the present invention comprises ahydrocarbon polymer having at least one alkenyl group per molecule. Itpreferably comprises a curing agent as well.

The above-mentioned hydrocarbon polymer having at least one alkenylgroup per molecule may be one similar to the (A) component of the primercomposition of the invention.

The curing agent mentioned above is not particularly restricted as faras it contains two or more hydrosilyl groups per molecule. Here, onehydrosilyl group means one SiH group, with the understanding that thecase in which 2 hydrogen atoms are attached to one and the same Si atomis counted as 2 hydrosilyl groups.

As the curing agent, an organohydrogen polysiloxane is one of thepreferred examples. The term “organohydrogen polysiloxane” as usedherein means a polysiloxane having hydrocarbon groups or hydrogen atomson silicon atoms, which includes the following acyclic and cyclicstructures, for instance.

2≦m+n≦50, 2<m, 0≦n, R is a hydroxycarbon group whose main chain contains2 to 20 carbon atoms and may have one or more phenyl groups.

0<m+n≦50, 0<m, 0≦n, R is a hydroxycarbon group whose main chain contains2 to 20 carbon atoms and may have one or more phenyl groups.

3≦m+n≦2 0, 2<m+n≦1 9, 0≦n<1 8, R is a hydroxycarbon group whose mainchain contains 2 to 20 carbon atoms and may have one or more phenylgroups.

Among the various hydrosilyl-containing groups mentioned above, thefollowing group is particularly preferred in view of the low likelihoodof reducing the compatibility of the hydrosilyl-containing curing agentof the invention with the hydrocarbon polymer.

2<k<1 0, 0<1<5, R is a hydrocarbon group containing not less than 8carbon groups.

The number of hydrosilyl groups to be present in such a curing agentneed only be at least 2 per molecule but is preferably 2 to 40, morepreferably 3 to 30. In causing the composition of the invention to cureby hydrosilylation reaction, the curing reaction is retarded to cause aninadequate cure when the number of hydrosilyl groups is less than 2. Onthe other hand, when the number of hydrosilyl groups exceeds 40, thestability of the curing agent is adversely affected and, in addition, alarge proportion of hydrosilyl groups remain in the cured product tocause voids and cracks in some cases.

In the curable composition to be used in accordance with the invention,the molar ratio of the alkenyl group in the hydrocarbon polymer to thehydrosilyl group in the curing agent is generally 1:0.5 to 1:5,preferably 1:0.8 to 1:3, still more preferably 1:1 to 1:2.5.

Furthermore, the curable composition to be used in the invention mayoptionally be supplemented with other components such as filler,antioxidant, ultraviolet absorber, pigment, surfactant, etc. as well asan adhesion-imparting agent for improving the adhesion of the curablecomposition. As examples of the filler, there can be mentioned inorganiccompounds such as titanium dioxide, zinc bloom, barium sulfate, etc. andorganic fillers such as polypropylene, polyethylene, polyacrylic estersand so on. As the adhesion-imparting agent, various silane couplingagents which do not deactivate the catalyst, such as epoxy, olefinic,methacrylic, ester, and tertiary amine series silane coupling agents canbe mentioned. Particularly, when the primer is coated on a substrate, itis not always necessary to impart adhesion to the curable compositionbut it does not matter whether adhesion is imparted to the curablecomposition or not.

The bonding method of the invention includes the following mode, amongothers.

(1) The primer composition is first coated on the surface of a substrateand the primer is cured within a temperature range of room temperatureto 150° C. for 1 minute to 60 minutes.

(2) Then, on the primed surface, an addition type curable compositioncomprising a hydrocarbon polymer is coated and cured in situ under thecuring conditions specific to the particular addition type curablecomposition of this hydrocarbon polymer.

The substrate includes aluminum, SUS, glass, polycarbonate, acrylicsheet, copperplate and so on.

The primer composition of the invention is expected to find applicationin a broad spectrum of uses exploiting its low moisture permeability,low hygroscopicity, low gas permeability, high heat resistance, highweather resistance, dielectric properties and shock absorbingproperties, for example sealants, gaskets, adhesives, sealing-pottingagents, various types of coatings, vibration dampers, and so on. Thoughsuch specific uses are not particularly restricted, there can bementioned, among others, gaskets/sealants for capacitors, lithium cells,fuel cells, batteries, chemical plants, engines, fuel tanks, etc.,architectural sealants, outdoor gaskets for roof water-proofing or solarcell sealing and other purposes, packings for pipes, electric circuitsealing boxes, packings for the caps of industrial cans, food cans andbottles, etc., or packings for ink cartridges and other high-performanceink materials, electronic circuit surface protective coatings, surfacecoatings for IC and other card materials, aluminum or other packingmaterials requiring chemical resistance for fuel cells and the like,sound-barrier or vibration damping sheet materials, roll materials formachinery and electric machinery, pipes for gases such as hydrogen andoxygen, and sealants for joints.

EXAMPLES

The following examples illustrate the present invention in furtherdetail, it being to be understood that the scope of the invention is byno means defined thereby.

Examples 1 and 2 Comparative Example 1

According to the formulas shown in Table 1, primer compositions ofExamples 1 and 2 and Comparative Example 1 were prepared.

These primer compositions were prepared by the following procedure. As(A) component, the allyl-terminated polyisobutylene having a molecularweight of about 10000 (product of Kaneka Corporation; EP400A) assynthesized in accordance with Japanese Kokai Publication Sho-63-105005was dissolved in hexane. Then, a silane coupling agent comprising3-glycidoxypropyltrimethoxysilane, vinyltrimethoxysilane and3-methacryloxypropyltrimethoxysilane as (B) component, Ethyl Silicate 40(product of Nippon Colcoat Co.) as (C) component tetra-n-butyl titanateas (D) component, polyvalent alkoxysilane condensate, andplatinum-vinylsiloxane complex catalyst (8.3×10⁻⁵ mmol/μl, 3 wt. % inxylene) as (E) component were added and mixed.

On the other hand, an addition reaction type polyisobutylene curablecomposition was prepared by the following procedure and an adhesion testwas carried out using the composition.

Thus, 100 g of an allyl-terminated polyisobutylene having a molecularweight of about 10000 (product of Kaneka Corporation; EP400A) wasblended with 5 g of methylhydrogen polysiloxane (product of KanekaCorporation; CR100). Then, 30 g of the plasticizer PAO5010 (product ofIdemitsu Petrochemical Co.), 1 g of the antioxidant MARKAO-50 (productof Adeka-Argus), and 26 g of the filler hydrophobic-treated wet silicawere mixed thoroughly by hand mixing and, using a 3-roller paint roll,the mixture was kneaded 3 times. To the resulting formulation were added55.9 μL of platinum-vinylsiloxane complex catalyst (8.3×10⁻⁵ mmol/μl, 3wt. % in xylene) and 25.1 μL of dimethyl maleate (product of Wako PureChemical), followed by hand mixing to prepare an addition reaction typepolyisobutylene curable composition.

As a test for tensile adhesion, the primer composition was coated onceon SUS304 or aluminum and heated at 110° C. for 30 minutes for coatformation. On this primed surface, the above curable composition wascoated in a thickness of about 3 mm and cured at 60° C. for 40 minutes.After curing, a manual peeling test was carried out with the bondedsurface being incised with a cutter knife. The substrate surface, afterpeeling, was observed to see whether the bond failure was cohesivefailure (CF) or adhesive failure (AF). The results are shown in Table 1.

TABLE 1 Compar. Primer formulation Ex. 1 Ex. 2 Ex. 1 (A) EP400A 10 10(B) 3-Glycidoxypropyl-trimethoxysilane 1 2 1 Vinyltrimethoxysilane 0.5 10.5 3-Methacryloxypropyl- 0.5 1 0.5 trimethoxysilane (C) Ethyl Silicate40 2 4 2 (D) Tetra-n-butyl titanate 2 4 2 (F) Platinum-vinylsiloxanecomplex 10 10 10 catalyst (G) Hexane 100 100 100 Adhesiveness AL CF100CF100 AF100 SUS304 CF100 CF100 AF100 CF100 represents 100% of CF, andAF100 represents 100% of AF.

The following is an example of production of the (E) component vinylcopolymer.

Production Example

A reactor equipped with a stirrer, thermometer, nitrogen gas inlet pipe,drip funnel and cooling jacket was charged with 50 g of toluene and thetemperature was increased to 110° C. Then, a solution composed of 30 gof stearyl methacrylate, 70 g of γ-methacryloxypropyltrimethoxysilane,0.5 g of 2,2′-azobis(2-methylbutyronitrile) and 50 g of toluene was fedto the reactor continuously over 3 hours. After completion of monomercharging, the polymerization reaction was further continued for 2 hoursto give a silyl group-containing vinyl polymer with a nonvolatilefraction of 50 weight % and a GPC (polystyrene equivalent) numberaverage molecular weight (Mn) of 15,000.

Examples 3 to 7 Comparative Example 2

According to the formulas shown in Table 2, primer compositions ofExamples 3 to 7 and Comparative Example 2 were prepared.

The primer compositions were prepared by the following procedure. To the(E) component vinyl polymer synthesized in Production Example were addedthe silane coupling agent comprising 3-glycidoxypropyltrimethoxysilane,vinyltrimethoxysilane and 3-methacryloxypropyltrimethoxysilane as (B)component, the polyvalent alkoxysilane condensate Ethyl Silicate 40(product of Nippon Colcoat Co.) as (C) component, tetra-n-butyl titanateas (D) component, and platinum-vinylsiloxane complex catalyst (8.3×10⁻⁵mmol/μl, 3 wt. % in xylene) as (F) component, and after mixing, thesolvent was added. When the (A) component was to be added, the (A)component was dissolved in hexane and added as such.

The evaluation of adhesion was made by the method described above. Theresults are shown in Table 2.

TABLE 2 Example Compar. Ex. Primer formulation (weight parts) 3 4 5 6 72 (E) Vinyl polymer* 30 50 70 50 50 (A) EP400A 5 10 (B)3-Glycidoxypropyl- 1 1 1 1 1 1 trimethoxysilane Vinyltrimethoxysilane0.5 0.5 0.5 0.5 0.5 0.5 3-Methacryloxypropyl- 0.5 0.5 0.5 0.5 0.5 0.5trimethoxysilane (C) Ethyl Silicate 40 2 2 2 2 2 2 (D) Tetra-n-butyltitanate 2 2 2 2 2 2 (F) Platinum-vinylsiloxane 10 10 10 10 10 10complex catalyst (G) Hexane 100 100 100 100 100 100 Adhesiveness SUS304CF CF CF CF CF AF Al CF CF CF CF CF AF (*): 50 weight % toluene

Examples 8 to 17 Comparatives 3 to 5

According to the formulas shown in Tables 3, 4 and 5, primercompositions of Examples 8 to 17 and Comparative Examples 3 to 5 wereprepared.

These primer compositions were prepared by the following procedure. Thesilane coupling agent comprising 3-glycidoxypropyltrimethoxysilane,vinyltrimethoxysilane and 3-methacryloxypropyltrimethoxysilane as (B)component, the polyvalent alkoxysilane condensate Ethyl Silicate 40(product of Nippon Colcoat Co.) as (C) component, tetra-n-butyltitanateas (D) component, and platinum-vinylsiloxane complex catalyst (3 wt % inxylene) as (F) component were mixed together and a suitable amount ofhexane as (G) component was then added.

The evaluation of adhesion was made by the method described above. Theresults are shown in Tables 3, 4 and 5.

TABLE 3 Example Compar. Ex. Primer formulation (weight parts) 8 9 10 113 4 (B) 3-Glycidoxypropyl- 1 2 1 1 1 0 trimethoxysilaneVinyltrimethoxysilane 0.5 1 0.5 0.5 0.5 0 3-Methacryloxypropyl- 0.5 10.5 0.5 0.5 0 trimethoxysilane (C) Ethyl Silicate 40 2 4 2 0 (D)Tetra-n-butyl titanate 10 10 0 0 (F) Platinum-vinylsiloxane 10 10 10 100 complex catalyst (G) Hexane 100 100 100 100 100 100 AdhesivenessSUS304 CF CF CF CF AF AF Al CF CF CF CF AF AF

TABLE 4 Ex. Primer formulation (weight parts) 12 (B) 3-Glycidoxypropyl-1 trimethoxysilane Vinyltrimethoxysilane 0.5 3-Methacryloxypropyl- 0.5trimethoxysilane (C) Ethyl Silicate 40 (D) Tetra-n-butyl titanate (F)Platinum-vinylsiloxane complex 10 catalyst (G) Hexane 100 AdhesivenessFRP CF Polycarbonate CF Acrylic sheet CF

TABLE 5 Example Compar. Ex. Primer formulation (weight parts) 13 14 1516 17 5 (B) 3-Glycidoxypropyl- 1 1 1 0 trimethoxysilaneVinyltrimethoxysilane 0.5 0.5 0 3-Methacryloxypropyl- 0.5 0.5 0trimethoxysilane (C) Ethyl Silicate 40 2 2 2 2 2 0 (D) Tetra-n-butyltitanate 10 10 10 10 10 0 (F) Platinum-vinylsiloxane 1 1 1 0 complexcatalyst (G) Hexane 100 Adhesiveness Glass CF CF CF CF CF AF CopperplateCF — — — — AF

It is apparent from the above examples that by using the primercomposition of the invention, various substrates can be renderedsufficiently adhesive.

Thus, the present invention provides a bonding method insuring aremarkably improved adhesion of an addition type curable hydrocarbonpolymer composition to various substrates.

What is claimed is:
 1. A bonding method for bonding a cured product to asubstrate which comprises coating a primer composition comprising asilane coupling agent on a substrate, applying a curable compositioncomprising a hydrocarbon polymer having at least one alkenyl group permolecule onto the primed substrate, and curing the curable compositionto obtain the cured product bonded to the substrate, wherein the silanecoupling agent has at least one functional group selected from the groupconsisting of epoxy, methacryl, acryl, isocyanate, isocyanurate, vinyland carbamate groups, and wherein said hydrocarbon polymer having atleast one alkenyl group per molecule is a polyisobutylene polymer havingat least one alkenyl group terminally of its backbone and/or side chain.2. A bonding method for bonding a cured product to a substrate whichcomprises coating a primer composition comprising a silane couplingagent on a substrate, applying a curable composition comprising ahydrocarbon polymer having at least one alkenyl group per molecule ontothe primed substrate, and curing the curable composition to obtain thecured product bonded to the substrate, wherein the silane coupling agenthas at least one functional group selected from the group consisting ofepoxy, methacryl, acryl, isocyanate, isocyanurate, vinyl and carbamategroups, and wherein said curable composition further comprises a curingagent containing two or more silicon-bound hydrogen atoms per molecule.3. A bonding method for bonding a cured product to a substrate whichcomprises coating a primer composition comprising a silane couplingagent on a substrate, applying a curable composition comprising ahydrocarbon polymer having at least one alkenyl group per molecule ontothe primed substrate, and curing the curable composition to obtain thecured product bonded to the substrate, wherein the silane coupling agenthas at least one functional group selected from the group consisting ofepoxy, methacryl, acryl, isocyanate, isocyanurate, vinyl and carbamategroups, and wherein said primer composition further comprises anorganoaluminum compound and/or an organotitanium compound.
 4. Thebonding method according to claim 2, wherein said curing agent is apolyorganohydrogen polysiloxane containing two or more hydrosilyl groupsper molecule.
 5. The bonding method according to claim 1, 2, 3 or 4,wherein the silane coupling agent has at least one functional groupselected from the group consisting of epoxy, vinyl and (meth)acryloylgroups.
 6. The bonding method according to claim 1, 2, 3 or 4, whereinsaid primer composition comprises a polyvalent alkoxysilane and/or acondensation product thereof.
 7. The bonding method according to claim1, 2, 3 or 4, wherein said primer composition comprises ahydrosilylation catalyst.
 8. The bonding method according to claim 1, 2,3 or 4 wherein said primer composition comprises an organic solvent. 9.A laminate obtained by the bonding method according to claim 1, 2, 3 or4.